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Trip report: Internal scuznet install in an SE

Posted by: cheesestraws on 2022-02-20 13:47:54

I have an SE that contains a Radius 020 accelerator. Further PDS expansion on top of the accelerator would have to happen through the MagicBus slot, and there was never an Ethernet card that plugged into that slot. I also had one of @saybur's scuznet boards (built by @aladds), so today @joshc and I rigged it up internally in an only moderately heath-robinson fashion using mostly bits that were hanging around, with only a tiny bit of (optional) soldering. This thread notes how we did it.

Here's the scuznet setup:

SCSI was provided to the scuznet through an internal-to-external adapter and a standard 25-pin D-sub gender changer, as found on—I think—eBay.

Power was a molex socket taken from an old fan adapter, with the 5V and ground wires screwed into a screw terminal to barrel jack adapter—once again, sourced from eBay some time ago.

The only soldering we had to do is to tack on wires for an external activity LED, replacing the activity LED on the board.

This whole affair mounted onto the hard disc sled (this is the machine with the pink hard disc sled) with sticky nylon standoffs which aren't quite straight because I'm slapdash.

To get Ethernet out to the back panel of the machine, I got a panel mount CAT6 extension lead that looks like this:

Panel Mount Extension Cables (50cm)

Need to expose HDMI, Ethernet, or USB to the outside of your project/enclosure? These lovely little 50cm panel mount extension cables are just the job!

shop.pimoroni.com

(though I can't remember if I actually got it from there or from eBay).

Some time ago, I designed a PCB backplate that will screw onto the expansion slot opening in the back of the SE, and take this extension lead:

Gerbers for this are available at https://github.com/cheesestraws/misc/tree/master/scuznet-mac-se-backplate. Do as you will with them.

Inside the machine, this all looked like this (yes, a shorter Ethernet cable would have been good):

And with the back on, it looks like this:

Posted by: Crutch on 2022-02-20 14:45:22

Very nice. I feel like I should know what MagicBus is, yet I do not. Pray tell?

Posted by: cheesestraws on 2022-02-20 15:12:29

I feel like I should know what MagicBus is, yet I do not. Pray tell?

MagicBus is a smaller expansion connector (which is basically PDS missing a few pins) that Radius invented so you could have a graphics card and an accelerator in the same SE, I assume because there's not room for two "normal" PDS cards (though I also assume the vendor lock-in didn't hurt). It sticks up through one of the holes in the SE chassis. If you didn't have an accelerator, you had a MagicBus "jumper card", which is just a passive adapter in a PDS card form factor which converts one to the other.

Posted by: superjer2000 on 2022-02-20 17:56:13

I have an SE that contains a Radius 020 accelerator. Further PDS expansion on top of the accelerator would have to happen through the MagicBus slot, and there was never an Ethernet card that plugged into that slot. I also had one of @saybur's scuznet boards (built by @aladds), so today @joshc and I rigged it up internally in an only moderately heath-robinson fashion using mostly bits that were hanging around, with only a tiny bit of (optional) soldering. This thread notes how we did it.

I had mentioned the same approach re: the panel mount cables in the Scuznet thread but in the context of having a Scuznet with an IDC50 connector to avoid needing to piece together the various adapters. I don't have the skills to modify the Scuznet to sport an IDC 50 instead but if somebody was able to make that change, that would open up a lot of possibilities (Very inexpensive HD/Ethernet adapter that would work great internally and with the Vonet can be adapted to Wifi.

On those panel mount cables, they are great for making Ethernet accessible externally for the Uthernet II cards on the Apple II.

Posted by: aladds on 2022-02-21 15:10:45

Very nice! I especially like the rj45 backplate

I do have a plan to do a re-spin of the Scuznet board with an IDC50 connector on it at some point, but I'm halfway through moving house and three other projects at the moment so hopefully I'll get some time next month!

Posted by: cheesestraws on 2022-02-22 12:29:31

I do have a plan to do a re-spin of the Scuznet board with an IDC50 connector on it at some point

Without meaning to back-seat drive, might I suggest that another good addition for this would be an HD activity LED header, mirroring the LED on the board? Good luck with the house move, always stressful...